Project 4 is a new project of HL 42550, whose long-term objective is to delineate the mechanisms that are responsible for the recent observation that pro-inflammatory cytokines that signal through the tumor necrosis factor (TNF) receptors or the gp130 family of receptors confer cytoprotective /anti-apoptotic effects in cardiac myocytes. To this end the immediate specific objectives of Project 4 will be to delineate the mechanisms for the cytoprotective effects of these cytokines in the setting of experimental myocardial ischemia/reperfusion (I/R) injury. Specific Aim 1 will test the hypothesis that reactive oxygen intermediates induced during I/R injury in mice are responsible for provoking cardiac myocyte apoptosis through mitochondrial dysfunction, release of cytochrome c, increased activity of caspases 9 and 3, and DNA degradation. Specific Aim 2 will test the hypothesis that TNF protects against I/R induced myocyte apoptosis by attenuating and/or preventing mitochondrial dysfunction, by examining the effects of I/R injury in transgenic mice with low levels of cardiac restricted over-expression of TNF and knockout mice both TNF receptors. Specific Aim 3 will test the hypothesis that the cytoprotective effects of TNF are mediated by TNF receptor associated factor 2 (TAF2), by examining the effects of I/R injury in transgenic mice with conditional over-expression of a TRAF2 dominant negative construct. Specific Aim 4 will test the hypothesis that activation of the gp130 pathway protects the adult cardiac myocyte against I/R induced apoptosis by attenuating the activity of caspases 9 and 3, and that the cytoprotective effects of the gp130 injury in transgenic mice with cardiac restricted expression of leukemia inhibitory factor and mice with a ventricular restricted knockout of gp130. The above studies will be conducted in a Langerdorff buffer perfusion model of global I/R injury, a closed-chest model of I/R injury, and in isolated murine cardiac myocyte model subjected to hypoxia/reoxygenation. Taken together, these studies will provide definitive new information with regard to the basic mechanisms responsible for the cytoprotective effects of pro- inflammatory cytokines following I/R injury.